Wang Yu-Xin, Clerk Aashish A
Pritzker School of Molecular Engineering, University of Chicago, 5640 South Ellis Avenue, Chicago, IL, 60637, USA.
Nat Commun. 2021 Nov 11;12(1):6528. doi: 10.1038/s41467-021-26868-7.
Quantum sensing protocols that exploit the dephasing of a probe qubit are powerful and ubiquitous methods for interrogating an unknown environment. They have a variety of applications, ranging from noise mitigation in quantum processors, to the study of correlated electron states. Here, we discuss a simple strategy for enhancing these methods, based on the fact that they often give rise to an inadvertent quench of the probed system: there is an effective sudden change in the environmental Hamiltonian at the start of the sensing protocol. These quenches are extremely sensitive to the initial environmental state, and lead to observable changes in the sensor qubit evolution. We show how these new features give access to environmental response properties. This enables methods for direct measurement of bath temperature, and for detecting non-thermal equilibrium states. We also discuss how to deliberately control and modulate this quench physics, which enables reconstruction of the bath spectral function. Extensions to non-Gaussian quantum baths are also discussed, as is the application of our ideas to a range of sensing platforms (e.g., nitrogen-vacancy (NV) centers in diamond, semiconductor quantum dots, and superconducting circuits).
利用探测量子比特退相的量子传感协议是用于探测未知环境的强大且普遍的方法。它们有多种应用，从量子处理器中的噪声抑制到关联电子态的研究。在此，我们基于这样一个事实讨论一种增强这些方法的简单策略，即这些方法常常会导致被探测系统的意外猝灭：在传感协议开始时环境哈密顿量存在有效的突然变化。这些猝灭对初始环境状态极其敏感，并导致传感器量子比特演化出现可观测的变化。我们展示了这些新特性如何能够获取环境响应特性。这使得能够直接测量热库温度以及检测非热平衡态。我们还讨论了如何有意地控制和调制这种猝灭物理过程，这能够重建热库谱函数。同时也讨论了向非高斯量子热库的扩展，以及我们的想法在一系列传感平台（例如金刚石中的氮空位（NV）中心、半导体量子点和超导电路）中的应用。
